Mechanistic study of the anodic electrochemiluminescence of luminol at platinum electrode

The behavior of anodic electrochemiluminescence (ECL) of luminol in alkalin e solution at a polycrystalline platinum electrode was studied. It was foun d that the ECL intensity and peak shape were related to pre - polarization of the platinum electrode and oxygen dissolved in the solution. Furthermore , the surface state of platinum electrode was detected under different cond itions by XPS and CV characteristics of Pt and Pt \ S-ads electrodes. The p ossible mechanism for the two anodic ECL channels is proposed: (1) Two cond itions are necessary for formation of the anodic ECL shoulder peak at 0.22V (vs.Ag). One is the oxygen dissolved in solution and another is that there are fresh Pt atom sites on the electrode surface. The luminol anion is elec tro - oxidized to luminol radical, which can react with dissolved oxygen to generate light emission. (2) Platinum oxides on the electrode surface can accelerate the producing rate of atomic oxygen. This leads to the enhanceme nt of ECL intensity of the peak near 0.60V(vs.Ag).